This project will continue studies on the effects of vestibulo-toxic aminoglycoside antibiotics on the dynamics of human vestibulo-ocular reflex (VOR) and vestibulo-spinal (VS) systems. The adaptive properties of the VOR and VS systems will be studied in patients who suffer vestibular ototoxicity. Conventional techniques, including caloric, saccadic eye movement, and optokinetic (oculamotor screening) tests will be performed in addition to rotational VOR and moving platform/visual surrounds VS tests. These VOR and VS test methods will be employed in various combinations in order to accomplish the project's specific aims. Results of this project will significantly advance the health care of patients who must receive life-saving ototoxic antibiotics by: 1) detecting ototoxicity at onset; 2) determining risk for ototoxicity at onset of treatment; 3) determining relative incidence of vestibular ototoxicity for the more commonly used aminoglycosides; and 4) characterizing adaptive motor reflex mechanisms in patients with vestibular ototoxicity. The development of rehabilitation strategies for subjects who became severely ototoxic will be enhanced by an improved understanding of adaptive motor reflex mechanisms.